Hydraulic motor directional control valve assembly



United States Patent 1111 3,533,440

[72] Inventors SamMaxBerr) [56] ReferencesCited Corinth, Mississippi: UNITED STATES PATENTS lll A PPLNU- 751194 2,910,971 11/1959 Mucouff 13T/625.66 i221 Filed ^g8-1968 3.013.539 1211961 1161111116161. 13T/625.63 i451 Pamd 0f13197 3.060.969 10/1962 Aslan 13T/625.63

[73| Assignee Kinematcks Inc., Pickwick Dam, Tenn. l

Prlmary Examiner-Henry T. Klinkslek .slimmer-Robertson, Bryan, Purmelee und Johnson ABSTRACT: The present invention provides a hydraulic motor directional control vulve assembly for controlling the [54] DIREC HONAL ('ONTROL rute und direction of movement of hydraulic motors. The control vulve assembly is adapted t0 be mounted on u multipluce l5 Claims 6 Drawing F'gs' hydraulic pump and to be connected to the input of the [52] U.S. Cl IS7/596.18 hydraulic motors. By means of the directional control vulve [51 l M- Cl s s Flk 11/10 assembly an operator can control u series of motors simultane- [50] Field of Search., l 37/59614. ously at variable speeds in forward and reverse directions. and

596.15, 596.18.625.6,6256162568 :it constant` full, intermediate, and maximum speeds.

Patented oct. 13, 1970 l 3,533,440

Sheet L of 4 INVENTOR. ,Slam M eifg/ BY Tron/Midi.

Patented Oct. 13,-1'970 Sheet 2 of 4 Patented Oct. 13, 1970 'Sheet 3 of 4 mw Nm NQ. SMH uw INVE TOR. 5am lll. 5er/"gf Q 1.1M l lv W 1 :www -www H -n II@ S }-liw|- 1mmlllu 1|Af Patented Oct. 13, 1970 S. Y R. a@ w o .1 R m w a E Mg. M, @NJ www H m f 5 NS# w HYDRAULIC MOTOR DIRECTIONAL CONTROL VALVE ASSEMBLY The present control valve assembly includes a series of valves. In the housing of the individual valves, there are ports adapted to be connected to the output of a hydraulic pump, inlets adapted to be connected to a fluid power source, and outlets adapted to be connected to the input of hydraulic motors. There are a series of adjoining cylinders formed within the housing. Within at least one of the cylinders there is a main piston rod slidably mounted and a valve spool operatively associated with the main rod for controlling the fluid within the valve from the hydraulic pump. Control pistons are slidably mounted in cylinders adjoining the cylinder in which the main rod is mounted. The control pistons are arranged in an end to end relation to the main piston rod to longitudinally displace the rod in either direction. Fluid control means are provided for controlling the transmission of fluid through the valve and to the hydraulic motors.

BACKGROUND OF THE INVENTION Various types of control valves have been designed to regulate and control the transmission of a hydraulic fluid from a pump to a hydraulic motor. Accordingly, these valves control the movement of a motor at a predetermined rate. These valves are generally limited in that the movement of the motor may only be in one direction and the rate is restricted to a certain range.

Generally, the valves and valve units have been limited in the extent of their control of motors and have been cumbersome in operation in that they may require a great deal of space and care in being installed in a hydraulic line between a pump and a motor. In contrast, the present control valve is small in size and may be utilized to control the rate and direction of movement of not only one motor but a series of motors, In providing these desired characteristics, the present valve assembly is simplified and durable, and yet reliable SUMMARY OF THE INVENTION This invention relates to a hydraulic motor directional control valve assembly. More particularly, it relates to a valve assembly for controlling the direction and rate of movement of a series of motors during operation. The valve assembly is adapted to be mounted in a multiplace hydraulic pump. The valve assembly includes aseries of valves. Each of the individual valves comprises a housing having ports adapted to be connected to each place on said pump, inlets adapted to be connected to a fluid power source and outlets adapted to be connected to the hydraulic motors. Within the housing there are a series of adjoining cylinders longitudinally arranged therethrough. A main piston rod is provided which is slidably disposed within at least one of the cylinders and is arranged to move longitudinally in either direction therein. At each end of the main piston is a control piston slidably disposed in an adjoining cylinder to longitudinally displace and shift the main rod. Fluid control means are provided which are associated with the main rod to control and transmit the fluid through the valve and to the motor, thereby controlling the rate and direction of movement of the motors.

Among the advantages of the present invention, is that it enables an operator to control one fluid motor from a full for ward to a full reverse motion at a variable rate and control and maintain another motor at a constant speed, at a full forward or reverse, or intermediate speed.

The present valve assembly also enables an operator to reverse the direction of both hydraulic motors when controlled at an intermediate speed. By means of the present valve assembly, each motor can be controlled at a variable rate from full to reverse speed, or vice-versa; or from an intermediate speed in one direction to an intermediate speed in an i opposite direction` derstood from a consideration of the following description of the preferred embodiments for carrying out the invention, when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. l shows a control valve assembly' embodying the present invention, mounted on a two-place hydraulic pump, showing the return line from the valve assembly to the hydraulic pump inlet;

FIG. 2 is a longitudinal sectional view of the control valve assembly shown in FIG. I, taken along line 2-2. The valve spool is shown in a position for bypassing the fluid back to the pump without actuating the motors;

FIG. 3 is a partial sectional view of the valve illustrated in FIG. 2 showing the valve shifted fully in one direction, Le., to the left;

FIG. 4 is a partial sectional view of the valve shown in FIG. 2, showing the valve shifted fully in one direction and controlled back to an idling position;

FIG. 5 is a partial sectional view of the valve shown in FIG. 2, showing the valve shifted fully in one direction with the spool valve shifted fully in the opposite direction; and

FIG. 6 is a partial sectional view of another embodiment of the present valve in which cylinder pistons are provided in place of the main rod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. l, there is shown a control valve assembly, generally indicated by V, embodying the present invention which is mounted on a two-place hydraulic pump P. The pump P has formed within it annular cylinders 7A, 7B, 7C, and 7D, in which rotor shafts, such as 8A and 8B, are disposed centrally in the respective annular cylinders. On the rotor shafts 8A and 8B, there are fixed pistons 9A, 9B, 9C, and 9D which are arranged to transverse the respective cylinders in annular movement. A drive shaft I0 is provided for rotating the respective rotor shafts 8A and 8B by means of a pinion 10A on its end which is enmeshed with pinions 11A and 11B fixed on rotor shafts 8A and 8B, respectively. The pump P is provided with inlet passages l2 and outlet passages 13.

The valve assembly V includes two valves 14, I6, and a pair of relief valves l5 and 17. The valves 14 and 16 are respectively mounted on the pump places 18B and 18A. There are fluid passageways 19A and 19B extending between the respective valves 16, 14 and the pump places 18A and 18B. There is a return line 20 provided, extending from the pump P to the outlet 2l of the valve assembly V. It is noted that any number of valves can be connected to any number of pump places and can be controlled as desired in the same manner as the valve unit described hereinbelow.

Referring to FIG. 2, a longitudinal sectional view of the control valve assembly is shown. For the sake of simplicity, only one-half of the valve assembly will be described, .e. valve 14 and relief valve 15. The valve 14, in its general construction comprises a housing 22 which has an inlet port 24 for connection with the hydraulic pump P, outlets 26 and 28 adapted to be connected to hydraulic motors, and ports 30 and 32 which connect the respective valves 14, 16 to a common low-pressure return 34. In the housing 22, there is formed a series of adjoining cylinders 35, 36, 38 and 39. Within cylinders 36 and 38, a main piston rod 40 is slidably mounted.

There are shifting inlets 42 and 44, in the housing 22, adapted to admit fluid from an outside fluid power source (not shown) to shift the position of the valves 14, 16. At each end of the valves and housing 22, there are control inlets 46 and 48, which are adapted, by means of hydraulic lines 47 and 49, respectively,mto be connected to the outside fluid power Asource for providing fluid at an equal flow rate, i.e. the same volume per unit time.

The fluid may be transported from the fluid power source to the respective inlets by means ofa conventional fluid pressure circuit of hydraulic lines such a fluid circuit would include a fluid pump which supplies the fluid under pressure through a ,hand-operated control valve. Accordingly, as determined by the operation of the control valve, the fluid is transferred through hydraulic lines to the respective inlets.

A valve spool 50 is provided which surrounds the main rod 40. The valve spool 50 controls the power fluid from the hydraulic pump P within the valve. The valve spool 50 is held in an idle position by springs 52 and 54, as shown in FIG, 2, when there is no fluid applied to shifting inlets 42 and 44.

As shown in FIGS. 2 and 5, the springs 52 and 54, are respectively positioned within the cylinders 36 and 38, which surround and engage the main rod 40 at its opposite ends. The springs 52, S4 are arranged to resist the movement of the rod 40 and valve spool 50 when a control fluid is supplied through the respective shifting inlets 42, 44. The relation of the springs 52 and 54, the main rod 40, and the valve spool 50 will be described in detail below.

At opposite ends of the valve and formed in the housing 22, there are the adjoining cylinders 35 and 39 in which there are slidably positioned, control piston rods 60 and 62, respectively. There are pistons 61 and 63 fixed to the ends of the rods 60 and 62, respectively. The pistons 61 and 63 are positioned near the respective inlets 46 and 48.

The pistons 60 and 62 are retracted and held within the cylinders 35 and 39 by springs 64 and 66, respectively. The springs 64, 66 are maintained in position by guide washers 68 and 70 which are in turn held in place respectively by retaining rings 72 and 74.

In each of the washers 68 and 70, there are holes 69 and 71 which allow fluid to flow freely from the chambers 80, 81, 82 and 84 through outlets 86 and 88 (FIGS. 2 to 5). These outlets 86 and 88, by means of hydraulic lines 87 and 89, respectively, are adapted to be connected to a low-pressure return line (not shown). Thus, when there is any change in the volume of fluid within the valve, it is due to the controlling or shifting of the valve in position.

Referring to FIGS. 2 to 5, the springs 52 and 54 are retained in position around the main rod 40. For example, spring 52 is retained on one end by a washer 97 and the shoulder 98 on the piston rod 40 and the shoulder 99 on the valve spool 50 while on the other end it is retained by a washer 100 which in turn is held by a spring retainer 101 contained on the piston rod 40 by a piston 102 fixed to the rod 40 by a pin 103. Accordingly, spring 54 is held at one end by a washer 104 and the shoulder 105 on the piston rod 40 and the shoulder 107 on the valve spool 50, and on the other end by a washer 106 which is held by a spring retainer 108 contained on the rod 40 by a piston 110 fixed by a pin 111 to the rod 40.

The valve spool S0, as shown in FIG. 2, is a tube which surrounds the main rod 40. In the valve spool 50 there are cutouts or openings (not shown) which correspond in size and shape to the openings of the pump port 24 and the motor ports 26 and 28. The openings are spaced to provide the valve spool 50 with sealing surfaces which seal the respective openings of the pump and motor ports as required for the passage of a fluid. That is, the valve spool 50 is shifted in position to align its openings with the corresponding openings through which a fluid is to pass and its sealing surfaces over the other openings. For example, as can be seen in FIG. 2 and FIG. 4, the valve spool 50 is in an idle position and the sealing surfaces of the valve spool are aligned with the respective openings of the ports 24, 26, and 28. By admitting fluid into the shifting inlet 42, the valve spool 50 and the piston rod 40 are caused to shift to the left. When this occurs, an opening in the valve spool aligns with an opening of one of the ports, such as motor port 26. Thus, the power fluid is emitted from the valve through the port to a respective motor. The amount of fluid introduced into the motor, .e. the flow rate of the fluid, is determined by the size of the orifice provided by the opening of the valve spool 50 and it position with the respective motor port. Ac-

cordingly, with a smaller orifice, the flow rate of the power fluid to the motor will be low, while a larger orifice will provide a greater fluid flow rate to the motor. Thus, the rate at which a motor is to run can be controlled as well as its direction of movement.

The rod 40 and valve spool 50 are shifted and placed in position by the fluid being admitted to the shifting inlets 42 and 44 and control inlets 46 and 48. When the rod and valve spool have been positioned, then the direction of flow as well as the flow rate of the fluid is controlled by which port or ports the openings of valve spool are aligned and the size of the orifice provided by such alignment for the fluid to flow through. In other words, by having the valve spool shifted to a certain position, the flow rate of the fluid may be a maximum whereas at another position it may be at a minimum or nonexistant.

As can be seen in FIG. 2, the relief valves 15 and 17 are common differential spool-type relief valves which are incorporated into the housing 22 and are interconnected to high and low pressure fluid sources by passageways and 92 respectively.

In the individual relief valve, for example, valve I5, there is one portion 94 of the valve spool 96, having greater differential diameter than a second portion 95, and when pressure is applied it tends to take hold of the differential and move the valve spool 96 to the left. Thus, the pressure fluid in passageway 90 is permitted to pass around the end of the valve spool 96 and out the bypass passageway 92 into the low pressure return 34 (FIG. 2).

In each of FIGS. 3, 4, and 5, there is shown a partial section ofa valve to show the various positions which a valve may take in controlling the transmission of fluid to a motor to control its direction and rate of movement, Washers 97 and 104 are omitted from FIGS. 3, 4, and 5 to simplify the drawings when describing the principle of operation.

FIG. 3 is a longitudinal section taken through the control valve 14 shown in FIGS. 1 and 2, which has been shifted all the way in one direction, i.e., to the left. The position of the valve is shifted due to the location, Le., the particular inlet or port at which a fluid is admitted or supplied to the valve, and the amount thereof. In this case, the fluid has been admitted through shifting inlet 42 and has passed through the passageway 112 in the cylinder 36. This action in turn actuates the valve spool 50 and the piston rod 40 to move to the left, as shown in FIG. 3. The shift in position to one direction is due to the fact that the area of the piston 102 is larger than the area of the face 114 of the valve spool 50, thus resulting in a force sufficient to overcome the force of the resistant springs 52 and 54. Generally, the piston rod 40 travels twice the distance the valve spool 50 does, and in the same direction, relative to the cylinders 36 and 38 in the housing 22. The movement of the piston rod 40 is limited in the distance it can travel by the piston 102, the spring retainer 101 and housing face 116 which together form an obstruction to prevent further movement ofthe rod 40, (FIG. 3).

As can be seen in FIGS. 3 to 5, the movement of valve spool 50 is limited by the face 114 of the valve spool 50, which with the spring retainer 101 and the piston 102 forms a solid. It is understood that the valve may be designed to any specification so that the rod 40 and the valve spool 50 can move any distances required to control the movement ofa hydraulic motOr.

It is noted that FIG. 3 is merely an illustration and by admitting the fluid through shifting inlet 44, the valve could be shifted fully in the opposite direction, Le., to the right. Also, the movement of the rod 40 and spool valve 50 would be limited by similar means. That is, the movement of rod 40 would be limited by piston 110, spring retainer 108 and housing face and the movement of the valve spool 50 would be limited by the valve spool face 126, retainer 108 and piston 110.

In FIG. 4, the valve 14 is shown, shifted all the way in one direction, i.e. to the left and has been controlled back one-half of the way of the total stroke of the valve spool 50, i.e. the

neutral or idle position thereof. This is accomplished by supplying equal volumes of fluid to both control inlets 46 and 48 within the housing 22. The fluid, coming into control inlet 46, by pressing against the piston 61 displaces the rod 60 which contacts the cylinder rod 40 at 130 and in turn displaces the cylinder rod to the right, as shown in FIG, 4. The valve spool 50 moves the same distance and in the same direction as the cylinder rod 40, since the fluid under pressure in the cavity 132 acts as a hydraulic link between the piston 110 and the valve spool face 126.

The fluid which is supplied to the inlet 48 and against the piston 63, moves the rod 62 the same distance as the rod 60 moves, and contacts the main rod 40 at 135. However, when the valve is shifted in the direction shown, the rod 62 serves no function. That is, when the-valve is shifted one-half of the way back, or to a neutral position, the piston rod 60 is in contact with the main rod 40 at 130 to displace it. lt is noted, that when the valve is controlled back to a neutral position, as shown in FIG. 4, and then is reversed in position, that the valve spool 50 would still be in the same position as shown in FIG. 4. It is only when the valve has been shifted or moved fully in one direction, either forward or in reverse, that the valve spool 50 is not in an idle or neutral position.

Referring to FIG. 5, the valve 14 has been shifted all the way to the left and has been controlled all the way in the opposite direction as it was shifted. As can be seen, fluid is admitted into the shifting inlet 42, through passageway 112 in the cylinder 36. This supply of control fluid causes the piston rod 40 as well as the spool valve 50 to move to the left. As can be seen, the distance the valve spool 50 and the main piston rod 40 can be controlled back is limited by the contact of the spring retainer 108 with the cylinder 136 in the cylinder 38 and face 126 on the valve spool 50.

Accordingly, the valves could be shifted fully in the opposite direction of that shown in FIG. 5, Le., to the right, by having the fluid admitted into the shifting inlet 44 and through the passageway 113 in cylinder 38. It also follows, that when the valve is moved fully in one direction and controlled fully to the opposite direction, and then is shifted in the opposite direction that the valve is automatically controlled to the opposite direction to which it had just been shifted.

In FIG. 6, there is shown another embodiment of the present invention which includes two cylinder pistons 150 and 152 which are spring pressed, by springs 154 and 156, respectively. As can be seen, the cylinder pistons are substituted for the main rod 40 (FIGS. 2-5) in the other embodiment of the present invention. In this embodiment, there are also additional inlets 158 and 160 which are connected by tubing 161 and 162 to the outside fluid power source. The fluid admitted through the inlets 158, 160, passes into annular cylinders 163 and 164, respectively. As shown, the fluid travels through passageways 166 and 168 to the respective ground out spaces 170 and 172, in which the cylinder pistons 150 and 152 are respectively mounted. With this arrangement, the individual cylinder pistons may be placed and held under pressure. By

having the cylinder pistons under pressure, the cylinder pistons 150 and 152 may be displaced to the right and left, respectively, by the force provided by the control pistons 174 and 176. As the cylinder pistons are moved, so is the valve spool 180 surrounding the cylinder pistons.

ln operation of this embodiment, fluid is admitted through the inlet 158 and passageway 166 to hold the cylinder 152 under pressure, as illustrated in FIG. 6. When the cylinder piston 152 is under pressure, fluid is admitted through the inlet 177 to actuate the control piston 176 which contacts the cylinder 152 and moves it to the left togetherwith the valve spool 180. The cylinder piston 150 is moved to the right in a like manner. That is, fluid is admitted through inlet 160 and passageway 168 to put the cylinder piston 150 under pressure. Then fluid is admitted through inlet 175 to actuate the control piston 174 which contacts the cylinder piston 150 to displace it with the valve spool 180 to the right.

It is noted in this embodiment, that the respective cylinder pistons must be kept under pressure in order to be actuated and thereby move the valve spool 180, accordingly. lf the cylinder pistons are not under pressure when the control pistons make Contact with them, only the cylinder piston itself is moved inward. The valve spool 180 remains stationary or in a neutral position. However, when the cylinder piston is under pressure as shown in FIG. 6, eg cylinder piston 152, the cylinder piston 152 may be moved to the left by the control piston 176, and thus, the valve spool 180 is moved to the left also.

In this embodiment, the main rod 40 is substituted by the pair of cylinder pistons and 152. By maintaining a cylinder piston under pressure and displacing it with a control piston, the valve spool can be moved either to the left or to the right. Accordingly, the openings in the valve spool 180 may be aligned with the openings of the pump port 182 and motor ports 184 and 186 for the passage of a fluid.

It is also noted, that the control pistons may be substituted, as shown in FIG. 6, by any suitable device which can be used to apply a force to move the cylinder pistons 150 and 152 along their longitudinal axis.

From the foregoing it is understood that the control valve y described above is well suited to provide the advantages and objectives set forth. It is noted, however, that even though 1. A hydraulic motor directional control valve assembly for controlling the rate and direction of movement of a series of hydraulic motors, said assembly including a series of valves which are adapted to be mounted on respective places of a multiplace hydraulic pump, each of said valves comprising:

a. a housing having a port adapted to be connected to said hydraulic pump, inlets adapted to be connected to a fluid power source, and outlets adapted to be connected to said hydraulic motors;

b. cylinders formed within said housing and extending longitudinally throughout said housing, said cylinders adjoining one another in an end to end relation;

c. a main rod slidably positioned within at least one of said cylinders, said rod being arranged to move longitudinally within said cylinder, said rod being oriented so that its axis coincides with that of said cylinder;

d. control piston rods slidably positioned in adjoining cylinbe activated by the fluid admitted through said port and said inlets; and b. springs mounted within said cylinder in which said main rod is positioned, said springs surrounding and engaging i said main rod.

3. A directional control valve assembly as set forth in claim 2, wherein said springs are mounted at each end of the main rod to resist its longitudinal movement.

4. A directional control valve assembly as set forth in claim 1, wherein said inlets within said housing are arranged to admit a fluid at equal flow rates to opposite ends of said valve to longitudinally displace said main rod and said valve spool.

5. A directional control valve assembly as set forth in claim 1, wherein the main rod has a piston affixed to each of its ends and slidably disposed in said cylinder.

ders to that which said main rod is positioned, said pistons 6. A directional control valve assembly as set forth in claim 2, wherein the main rod is arranged to move twice thedistance of that of the valve spool.

7. A directional control valve assembly as set forth in claim l, wherein the axis of the control piston rods coincides with that of said main rod.

8. A hydraulic motor directional control valve assembly for controlling the rate and direction of movement of a series of motors, said assembly including a series of valves adapted to be mounted on the respective places of a multiplace control pump, each of said valves comprising:

a. a housing having a port adapted to be connected to said hydraulic pump, inlets adapted to be connected to a fluid power source, and outlets adapted to be connected to said hydraulic motors;

b. cylinders formed within said housing and extending longitudinally throughout said housing, said cylinders adjoining one another in an end to end relation;

c. a main rod slidably disposed within at least one of said cylinders, said rod being arranged to move longitudinally within said cylinder, said rod being oriented so that its axis coincides with that of said cylinder;

d. control position rods slidably positioned in adjoining cylinders to that which said main rod is positioned, the axis of said control pistons coinciding with that of said main rod, and said control pistons being arranged to longitudinally displace said main rod;

e. a valve spool surrounding said main rod and operatively associated therewith to move in a similar manner; and

f. force means associated with said main rod and said valve spool to control the transmission of fluid within andthrough the valve to a hydraulic motor, whereby the direction and rate of movement of said motor is controlled.

9. A directional control valve assembly as set forth in claim 8, wherein the main rod is arranged to move twice the distance of that of the valve spool.

l0. A directional control valve assembly as set forth in claim 8, wherein said inlets in said housing are arranged to admit a fluid at equal flow rates to opposite ends of said valve unit to displace said main rod of said valve spool.

ll. A directional control valve assembly as set forth in claim 8, wherein the force means are springs mounted at each end of the main rod to resist its longitudinal movement in both directions.

l2. A hydraulic motor directional control valve assembly source, an outlet adapted to be connected to said hydraulic motors;

b. cylinders formed within said housing andextending longitudinally throughout said housing, said cylinders adjoining one another in an end to end relation;

c. spring-pressed cylinder pistons slidably mounted within at least one of said cylinders, said cylinder pistons being arranged to move longitudinally within said cylinders, and said cylinder pistons being oriented so that their axis coincides with that of said main cylinder;

d. hydraulic passages connecting said cylinder pistons with said fluid power source;

e. control pistons slidably positioned in adjoining cylinders to that which said cylinder pistons are mounted, said control pistons being aligned with said cylinder pistons to longitudinally displace said cylinder pistons; and

. fluid control means associated with said cylinder pistons to control the transmission of fluid within the valve to one of said hydraulic motors, whereby the direction and rate of movement of said hydraulic motor is controlled: l3.'A directional contro valve assembly as set forth in claim 12, wherein said fluid control means includes in part a valve spool operatively associated with said cylinder pistons to be actuated by the movement of said cylinder pistons within said main cylinder. v

14. A directional control valve assembly as set forth in claim '12, wherein said inlets within said housing are arranged to admit fluid of equal flow rates to opposite ends of said valve to longitudinally displace said cylinder pistons and said valve spool.

l5. A hydraulic motor differential control valve assembly for controlling the rate and direction of movement of a series of hydraulic motors, said assembly including a series of valves which are adapted to be mounted on respective places of a multiplace hydraulic pump, each of said valves comprising:

a. a housing having a port adapted to be connected to the hydraulic pump, inlets adapted to be connected to a fluid power source, and outlets adapted to be connected to said hydraulic motors;

b. cylinders formed within said housing and extending longitudinally throughout said housing, said cylinders adjoining one another in an end to end relationship;

c. at least two pistons slidably mounted within said cylinders, said pistons being arranged to move longitudinally within said cylinders;

d. control means positioning said pistons in response to control fluid;

e. a fluid control means positionable by the movement of said pistons to control the transmission of fluid within the valve and to one of said hydraulic motors, whereby the direction and rate of movement of said hydraulic motor is controlled. 

